What type of radiographs are filtered out by the aluminum disc within the PID?

The aluminum disc within the PID (Position-Indicating Device) is specifically designed to filter out long wavelength radiographs. Long wavelength radiographs, which are less energetic and have lower penetration capabilities, do not contribute to the diagnostic quality of the images and can increase the patient's radiation exposure without providing useful information.

By filtering out these long wavelengths, the aluminum disc helps ensure that only the higher energy, shorter wavelength radiographs are used, which are more effective for producing clear images on the dental radiographs while minimizing unnecessary radiation to the patient. This filtering process is essential for optimizing both the quality of the images produced and the safety of patients undergoing dental radiography.